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Ok, so we know that some finishes have drawback, IE Nitro and KTM-9 not standing up to some peoples acidic sweat, french polish/shellac not resisting alcohol etc.
Are there any known issues with urethane, either waterborne or solvent based?
Thanks

So far I've urethane on only one guitar so I don't have a lot of experience. However, I won't use it again on a neck. It has not stood up well and now the neck is no longer smooth.

Pat

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There are three kinds of people:

Those that make things happen,
those that watch things happen,
and those that wondered what happened.

Was it water or oil based?
How exactly is it not standing up well? You say it is no longer smooth. Has it blistererd or sunk into the pores or anything?
Thanks

Are you talking about a 2 component catalyzed (2K) urethane, or a single component like you can buy at Lowes or Home Depot? The single component stuff isn't very tough, or flexible. I use 2K urethane (ML Campbell Euro-bild, with their exotic woods sealer)on all my necks (unless the client wants something else) and some of my bodies. Some people use automotive clears that are a 2k urethane. The automotive stuff should have adhesion problems on wood, but there's people that I respect who report that it works great. Automotive urethanes are designed to be applied over the correct primers and base coats. 2K urethanes for wood are designed to be applied over the correct sealers. I've never stepped "outside the box" with either.

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I didn't mean to say it, but I meant what I said.
http://www.brackettinstruments.com/

Actually, I think it is a 2k urethane. I'm talking about KTM-SV specifically, but wondering what the achilles heel of urethane might be in general.
Thanks

A 2K urethane, or at least what I call one has to have a catalyst added, which makes it set up. I wouldn't call KTM-SV a urethane, but I see that Grafted Coatings does call it that. It's not a 2K urethane. I haven't used any, therefore I have no opinion. I have tried a couple waterbornes, and I've been dissappointed. KTM-SV may be different. Expecations may also vary.

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I didn't mean to say it, but I meant what I said.
http://www.brackettinstruments.com/

I just sprayed an automotive catalyzed urethane on a guitar about 3 weeks ago. First time not using nitro. I did test adhesion on some scrap panels first, and found that the adhesive qualities on bare wood are as good as or better than nitro. The advantages I see so far are less time to wait for leveling and buffing. The disadvantages are that you have less time to work with each mix, depending on the pot life, the stuff I used had 1 hour pot life. Plenty of time to put 2 coats on, repeated again the next day. One other disadvantage is that it seemed to take longer to buff out, but just may be that a different technique is needed as compared to nitro. Overall, the finish looks like a nitro job. I am not sure if I will use it again though, I think it would be difficult to repair/ touch up.

Chuck

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Ah yes,
KTM-SV is self crosslinking, so therefore not a 2k. My mistake.
Woody B, why would you not call it a Urethane? What exactly is urethane that KTM-SV would fail to be one?
I also have been disappointed with most waterbornes. I was liking ktm-9 until I started having durability issues. KTM-SV seems to spray just as easily, we'll have to see how it stands up.
Thanks

What I had used was the min-wax wipe-on polyurethane. If I remember correctly, I did around eight coats. Basically, I think it is just wearing off unevenly.

A couple of years ago Mario aka Grumpy said the same thing about urethane but I didn't pay attention. I should have.

Pat

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There are three kinds of people:

Those that make things happen,
those that watch things happen,
and those that wondered what happened.

I have been shooting McFaddens 2 part Urethane for several years. I really like it but the two main issues are its pretty tricky to spot repair and it [can] delaminate if dinged. Adhesion is MUCH better over a 2 part sealer.

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tim...
http://www.mcknightguitars.com

Well, I guess I'll find out anyhow. I've been looking for a waterborne finish because solvent based finishes aren't an option for me, and I've never really felt right about outsourcing it. So I've shot two guitars with KTM-SV, and we'll just have to see how it stands the test of time!
Thanks

I just finished spraying a second guitar with KTM-SV. I've taken Rolf Gerharde on his word that there have been no issues with instruments he's had out there in the real world for a couple of years. It sounds like a viable alternative to the other waterborne products and, as others have pointed out, has none of the blue cast SOME have reported with KTM9, USL, EM6000, etc.

As an aside, I'm pleased to note that after it's cured for a few days it can be sanded using water as the lubricant - unlike the other water-based offerings. That said, I found it impossible to polish out witness lines until it had been left for a couple of days following wet-sanding.

Cheers
Pete

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Cheers
Pete

For me the issue wasn't the blue tint, I would have lived with that if that was the only problem. The problem dfor me was that it blistered under my Ph balance. As well, I had to refinish a few of my past clients instruments for the same reason, two out of twenty or so that I did with KTM-9. Obviously if you're trying to get a fledgling business off the ground that's problematic, but otherwise I liked it. My understanding is that USL and EMTech 6000 are all acrylics as well. I kind of figured that whatever each particular brands' mix was, it was the actual substance carried in the water that was the problem.
Hopefully this SV will be different for me. It sprayed easily, and could (as you mentioned) be sanded level the next day using soap and water. I couldn't get past sanding with Micro-Mesh 1800 without weird little black balls forming, but I'll give it a week to cure and see what happens. If it doesn't blister under skin contact, I'll be very happy. But that was my original query, whether or not urethane is a durable finish.
Thanks all...

There are 2K urethanes and there are 2K urethanes. Not all are created equal. BTW the Minwax wipe on poly is a urethane resin supended in an oil and thinner base. It is not comparable to the solvent based 2K urethanes mentioned above.
Some 2K urethanes are self sealing, in that they don't need to be applied over a sealer. For example, the ILVA products I mention in my finishing DVD are self sealing but sealers can be purchased for them. The Euro build brand by Campbell's requires no sealer in their gloss or satin but is recommended for their wet look sheen. I used to use their gloss sheen with no sealer and buff it up to the high gloss sheen until the local store here sold me an outdated catalyst and then didnt want to stand behind their product. (R$&^!!!@UYTTF#$$&)*&*!!!!! were some of the words that came to mind at the time!) They have since stopped carrying the product due to customer complaints.
Anyway, 2K urethane is still one of my favorite guitar finishes for a number of reasons. It is tempermental and like any finish has its negative side but a very nice durable finish can be obtained using it.

Aha!
But what is the negative side?

You can blow yourself up or poison yourself.

I too am considering using KTM-SV on my first build......so I very much appreciate this thread (and similar ones).

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Formerly known as Adaboy.......

All 2K urethanes that I know of use isocyanate hardners. Isocynates are bad. Proper venilation and saftey equipment are a must. Reguardless of what finish anyone uses it's best to make sure the proper precautions are taken.

KTM-SV doesn't use an isocynate hardner. I'm not sure what equipment, and precautions are needed with it. Always check the MSDS and take care of yourself.

Me, not thinking of KTM-SV as a urethane probably has more to do with my knowledge of what's considered a "urethane", that the actual formulation.

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I didn't mean to say it, but I meant what I said.
http://www.brackettinstruments.com/

Well the very thorough MSDS indicates non-toxicity. Of course one has to avoid prolonged exposure to vapours as they 'may irritate eyes and throat' etc. They are particular about not getting it in the eyes.There's more of course, but if you buy some you'll get your own copies. It seems quite benign though.
I have tried several different waterbornes. This has been the easiest to spray, and I was able to sand flat the next day with 1500 grit micro-mesh. And that was a poorly applied spray session, my compressor is underated for my gun so full vaporization didn't occur. Throw in a little bit of the old lack of skill/experience and you've got a bit of a mess, runs on the top, pebbly back etc. And still it sanded out flat very easily, so I'm sure with a bit of practice application will become a breeze. Point being that it's very forgiving, so I would say give it a try on your first, why not? For me the hitch will be whether it stands the test of time, and unfortunately there is only one solution for that.
Cheers
PS As a bonus, you can't blow yourself up with this stuff, so setting up a booth is a lot less complicated...

Thanks meddlinfool. Still have a bit of work before I'm ready to spray.

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Formerly known as Adaboy.......

I liked it`s tuffness and don`t really care if I blow up.Thanks for that tip though Robbie. What I had problems with were witness lines.I couldn`t get to where I was satisfied and decided to buff it down to a satin finish.Which is okay ,but not what I was trying to accomplish.
James

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James W Bolan
Nashville Tennessee

James, are you describing your experience with 2K urethane or KTM-SV?

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Formerly known as Adaboy.......